This invention relates to the field of mounts for optical structures, including but not limited to, reflective panels, optical filters (absorptive and/or dichroic), hollow retroreflectors and solid retroreflectors.
Optical structures such as, but not limited to, reflective panels (mirror panels), optical filters (absorptive and/or dichroic), hollow retroreflectors and solid retroreflectors are old in the art. Solid retroreflectors are solid tetrahedrons of glass wherein three adjacent sides of the tetrahedron are substantially perpendicular to each other and these three sides that meet at a common corner are polished to have a high degree of flatness. Hollow retroreflectors are made of three mirror panels joined together preferably having optically flat reflective surfaces disposed at right angles to each other, and meeting at what can be described as a common inside corner of an imaginary cube. Both solid and hollow retroreflectors in general have the essential property of causing incident and reflected light rays to travel along substantially parallel paths.
When hollow retroreflectors are assembled for high accuracy and precision it is important to maintain the mutual perpendicularity of the reflective surfaces and sometimes essential to ensure that the retroreflector as a whole does not move. The perpendicularity of the reflective surfaces is affected by external stresses. With regard to high accuracy and precise reflective panels, such as mirror panels to be used for high accuracy purposes, it is also important to try to maintain as optically flat as possible the reflective surface of the panel.
Examples of external stresses that can affect the optical flatness of a reflective panel, an optical filter and/or the perpendicularity of reflective surfaces of abutting reflective panels of a hollow retroreflector, are thermal expansion or contraction of the substrate material from which the panels are made, deflection caused by curing of the adhesives used to join elements together and/or to join the retroreflector to its mount and/or the mass of the panels themselves. Accordingly, it would be desirable to assemble together the elements of a hollow retroreflector or of an optical filter, and/or to assemble a reflective panel to a mount, in such a manner as to reduce these stresses. It would also be desirable that the manner of mounting an optical filter, reflective panel(s) and/or a retroreflector to its mount not add to these stresses, but nevertheless, securely retain the optical filter, reflective panel(s) and/or retroreflector on the mount. Examples of hollow retroreflector mounts which have proven successful in maintaining the reflective surfaces in their perpendicular orientations are found in U.S. Pat. No. 3,977,765, to Morton S. Lipkins, U.S. Pat. No. 5,122,901, to Zvi Bleier, and U.S. Pat. No. 5,335,111, also to Bleier.
Additionally, any prior art mounts that may include flexible materials cannot, and do not, maintain the dimensional stability (“DS”) such that various forces working on a connected optical structure may be constantly changing the dimensions of that optical structure.
The present mount also achieves secure mounting of the optical structure in a manner designed to help eliminate deflective stresses on the reflective surface(s) of the structure caused by the mounting of the optical structure, such as the optical filter, the reflective panel(s) and/or the retroreflector to its mount. One or more aspects of the present mount also achieve dimensional stability (“DS”) such that a “hard mount” is achieved. One or more further aspects of the present invention permit the hard mounts to maintain any provided degree of flatness (e.g., at least about λ/4, at least about λ/10, between about λ/4 and about λ/30, etc.) and more particularly, to maintain a high degree of flatness (e.g., at least about λ/20, at least about λ/15, between about λ/15 and about λ/20, between about λ/15 and about λ/30, etc.) after the mount is constructed.
The mount also allows for easy and secure mounting of the optical structure onto a support structure.